A power window control apparatus mounted on a vehicle raises or lowers the door glass to a desired position by operating a glass raising/lowering mechanism by the drive of a motor. Since a raised or lowered position of the door glass can be calculated from the number of rotations of the motor, a control unit performs control by constantly detecting the rotational state of the motor (See Patent Document 1, for instance).
The rotational state of this motor is detected by a rotation detection sensor provided on a rotating shaft of the motor. The rotation detection sensor comprises, for example, a magnet whose north pole and south pole are oppositely disposed on a rotating shaft of the motor and hall elements that are disposed therearound. As the magnet rotates together with the rotating shaft of the motor, pulsing detection signals (hall voltages) proportional to the magnetic flux density are outputted from the hall elements. The rotational speed of the motor can be determined by calculating the rotation period of the motor from the pulse interval of the detection signals. In such a case, if two hall elements are disposed out of phase from each other relative to a single magnet for instance, then the rotational direction of the motor can also be detected by comparing the on and off states of the detection signals outputted from the two hall elements.
[Patent Document 1] (1) Japanese Patent Application Publication No. Hei11-107624.